Nasal obstruction in children is often caused by enlarged adenoids (tissues at the very back of the nasal space). Very rarely nasal obstruction may be caused by a benign or cancerous tumour inside the nose. Nasal obstruction can cause difficulties with breathing and may cause snoring and sleep difficulties leading to daytime tiredness. If nasal obstruction is present for more than four weeks it may be worth seeking medical help to diagnose the cause and discuss treatment options.